The present application relates to fabrication of interconnects having air gaps, and more particularly to structures and methods for preventing erosion of interconnects during an air gap formation process.
Integrated circuits (ICs) commonly use copper (Cu) interconnects to connect semiconductor devices such as, for example, transistors, on the ICs. As scaling of the IC chips continues, the distance between the adjacent interconnects decreases, and thus the resulting capacitance, which is a function of the dielectric constant (k value) of the insulating material divided by the distance between the adjacent interconnects, increases. This increased capacitance leads to increased capacitive coupling between the interconnects, thereby increasing power consumption and limiting the device speed. The use of an air gap between interconnects has been explored to reduce interconnect capacitance. However, all of the current airgap formation schemes run the risk of significant Cu erosion, which presents reliability issues. Therefore, a method that can effectively prevent erosion of interconnects during air gap formation remains needed.